UnreachableCodeWorker.java
/*
** Module : UnreachableCodeWorker.java
** Abstract : Helper routines for unreachable code processing rule-sets.
**
** Copyright (c) 2005-2022, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- ----------------Description-----------------
** 001 SIY 20050706 @21709 Created initial version.
** 002 SIY 20060312 @24992 Added support for NOT and parentheses in
** expression evaluator.
** 003 GES 20090518 @42382 Import change.
** 004 TJD 20220504 Java 11 compatibility minor changes
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
**
** 1. No License To Use Trademarks.
**
** This license does not grant any license or rights to use the trademarks
** Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
** of Golden Code Development Corporation. You are not authorized to use the
** name Golden Code, FWD, or the names of any author or contributor, for
** publicity purposes without written authorization.
**
** 2. No Misrepresentation of Affiliation.
**
** You may not represent yourself as Golden Code Development Corporation or FWD.
**
** You may not represent yourself for publicity purposes as associated with
** Golden Code Development Corporation, FWD, or any author or contributor to
** the covered work, without written authorization.
**
** 3. No Misrepresentation of Source or Origin.
**
** You may not represent the covered work as solely your work. All modified
** versions of the covered work must be marked in a reasonable way to make it
** clear that the modified work is not originating from Golden Code Development
** Corporation or FWD. All modified versions must contain the notices of
** attribution required in this license.
*/
package com.goldencode.p2j.convert;
import java.util.*;
import com.goldencode.ast.*;
import com.goldencode.p2j.pattern.*;
import com.goldencode.p2j.uast.*;
import com.goldencode.p2j.util.*;
/**
* Helper routines for the unreachable code processing rules. This provides
* support for constant resolution and for simple expression evaluation
* to statically determine if a particular conditional execution path can
* be proven to be unreachable.
*/
public final class UnreachableCodeWorker
extends AbstractPatternWorker
{
/** Expression evaluates to <code>false</code>. */
private static final long RES_FALSE = 2;
/** Expression evaluates to <code>true</code>. */
private static final long RES_TRUE = 1;
/** Expression cannot be evaluated statically. */
private static final long RES_UNKNOWN = 0;
/**
* Default constructor which initializes libraries.
*/
public UnreachableCodeWorker()
{
super();
setLibrary(new Helper());
}
/**
* Resolve constant name into its value.
*
* @param constant
* Name of the constant.
*
* @return Value for the known constant name or <code>null</code> if
* the name is unknown.
*/
public Object resolveConstant(String constant)
{
if("RES_FALSE".equalsIgnoreCase(constant))
return Long.valueOf(RES_FALSE);
if("RES_TRUE".equalsIgnoreCase(constant))
return Long.valueOf(RES_TRUE);
if("RES_UNKNOWN".equalsIgnoreCase(constant))
return Long.valueOf(RES_UNKNOWN);
return null;
}
/**
* Provides user-level APIs necessary for unreachable code processing.
*/
public class Helper
{
/** Information about known variables */
HashMap varPool = new HashMap();
/**
* Add a variable to the pool of known variables. A variable consists
* of a name and a list of values. If the variable is already known
* in the pool, then a new value is added to the array of known values.
* <p>
* At this time, all variables must be of type VAR_CHAR and the values
* must be the Java version of the Progress STRING.
*
* @param variable
* Variable name. Must not be <code>null</code>.
* @param value
* New variable value. Must not be <code>null</code>.
*
* @return <code>true</code> if operation was successful.
*/
public boolean addKnownVarValue(String variable, String value)
{
if (variable == null || value == null)
return false;
variable = variable.toLowerCase();
List data = (List)varPool.get(variable);
if (data == null)
data = new LinkedList();
data.add(value);
varPool.put(variable, data);
return true;
}
/**
* Try to evaluate the expression defined by the passed AST node. If
* this can be done then return result of evaluation.
* <p>
* At present only the following expressions are recognized:
* <p>
* <ol>
* <li>TRUE</li>
* <li>FALSE</li>
* <li>VAR_CHAR = STRING</li>
* <li>STRING = VAR_CHAR</li>
* <li>VAR_CHAR <> STRING</li>
* <li>STRING <> VAR_CHAR</li>
* </ol>
*
* @param node
* Expression root node.
*
* @return <code>RES_UNKNOWN</code> if the expression cannot be
* evaluated, <code>RES_TRUE</code> if the result is
* <code>true</code> and <code>RES_FALSE</code> if the result
* is <code>false</code>.
*/
public long tryEval(Aast node)
{
if (node == null ||
node.getType() != ProgressParserTokenTypes.EXPRESSION ||
node.getFirstChild() == null)
{
return RES_UNKNOWN; // Result is unknown
}
return tryEvalNode((AnnotatedAst) node.getFirstChild());
}
/**
* Try to evaluate CASE-WHEN-THEN statement expression which compares
* a <code>VAR_CHAR</code> to a <code>STRING</code>.
*
* @param var
* CASE statement variable name of type <code>VAR_CHAR</code>.
*
* @param value
* THEN statement value of type <code>STRING</code>.
*
* @return <code>true</code> if variable contains specified value.
*/
public boolean tryEvalCase(String var, String value)
{
List list = getKnownValues(var);
if (list == null)
return false;
value = character.progressToJavaString(value);
if (list.indexOf(value) >= 0)
return true;
return false;
}
/**
* Get list of known values of the variable for the expression
* evaluator.
*
* @param var
* Variable name (will be automatically translated to lower
* case).
*
* @return Array with the variable values or <code>null</code> if no
* such variable defined.
*/
private List getKnownValues(String var)
{
if (varPool == null)
return null;
return (List)varPool.get(var.toLowerCase());
}
/**
* Expression evaluation worker.
*
* @param node
* Expression root node.
*
* @return <code>RES_UNKNOWN</code> if the expression cannot be
* evaluated, <code>RES_TRUE</code> if the result is
* <code>true</code> and <code>RES_FALSE</code> if the result
* is <code>false</code>.
*/
private long tryEvalNode(AnnotatedAst node)
{
if (node == null ||
node.getNumberOfChildren() > 1)
{
return RES_UNKNOWN;
}
AnnotatedAst child = (AnnotatedAst) node.getFirstChild();
int type = node.getType();
if (child != null)
{
if (type == ProgressParserTokenTypes.LPARENS)
return tryEvalNode(child);
if (type == ProgressParserTokenTypes.KW_NOT)
{
long res = tryEvalNode(child);
if (res == RES_FALSE)
return RES_TRUE;
if (res == RES_TRUE)
return RES_FALSE;
return res;
}
return RES_UNKNOWN;
}
if (type == ProgressParserTokenTypes.BOOL_TRUE)
return RES_TRUE;
if (type == ProgressParserTokenTypes.BOOL_FALSE)
return RES_FALSE;
if (type == ProgressParserTokenTypes.EQUALS ||
type == ProgressParserTokenTypes.NOT_EQ)
{
boolean isEq = (type == ProgressParserTokenTypes.EQUALS);
AnnotatedAst tmp = (AnnotatedAst) node.getFirstChild();
if (tmp == null)
return RES_UNKNOWN;
String var = null;
String data = null;
while (tmp != null)
{
int ttype = tmp.getType();
if (ttype == ProgressParserTokenTypes.VAR_CHAR)
var = tmp.getText();
if (ttype == ProgressParserTokenTypes.STRING)
data = character.progressToJavaString(tmp.getText());
tmp = (AnnotatedAst) tmp.getNextSibling();
}
if (var == null || data == null)
return RES_UNKNOWN;
List list = getKnownValues(var);
if (list == null)
return RES_UNKNOWN;
if (list.indexOf(data) >= 0)
return isEq ? RES_TRUE : RES_FALSE;
return isEq ? RES_FALSE : RES_TRUE;
}
return RES_UNKNOWN; // Result is unknown
}
}
}